Epc is an error-propagating calculator, designed to help you evaluate
formulas that are based on uncertain quantities. For example,
the input

$x = 10 +- 1;
calculate 2 * $x;

produces an indication that the result is 20 +- 2, as expected, while
the input

$pi = 3.14159 +- 1;
calculate sin($pi/2);

tells you something that might be harder for you to calculate
yourself, i.e. that the error bar ranges from 0.78 to
1.0.

In trying to get the gist of what epc provides, note
that traditional estimates of error bars have difficulty with the
sin function, which cannot exceed 1. Also, note
that the lower-limit on the error bar on sin(x) is not the
same as the sin of the lower limit on x.)

Epc works by monte-carlo calculations of a given
formulae, randomly perturbing parameters with a distribution matched
to the error bars. The estimate of the result derives from analysis
of the probability density function of the results of the trial
calculations. For details of how epc works, and how to
use it, see the online manual.

Epc is written in Perl, although if it becomes more
popular, it might be rewritten as a compiled application, which would
make it 1 or 2 orders of magnitude faster.